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SOUTHEASTERN GEOLOGYV. 45, No.4, August 2008, p. 225-232
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ABSTRACT
The Carolina Terrane has yielded veryfew Ediacaran-age fossils. These includedPteridinium carolinaensis, cf. ?Swartpuntiasp. and a variety of trace fossils. Recent col-lecting efforts in the Albemarle Group haveyielded Sekwia excentrica from the FloydChurch Formation, an indeterminate sac-like organism from the unnamed MudstoneMember of the Cid Formation, Stanly Coun-ty and Aspidella cf. A. terranovica from theunnamed Mudstone Member of the Cid For-mation, Davidson County, North Carolina.North Carolina Ediacara biota, though con-sidered deep-water, has greatest affinity withthe Nama assemblage of similar age.
INTRODUCTION
Ediacaran-age fossils are known from ap-proximately thirty localities on five differentcontinents (Narbonne, 2005). A number ofstudies have focused on what their distributionspatterns reveal about paleogeographic recon-structions (McMenamin, 1982; Donovan, 1987;Waggoner, 1999, 2003; Hagadorn and Wag-goner, 2000), paleoenvironments, paleoecolo-gy, and taphonomy (Grazhdankin and Ivantsov,1996; Gehling, 2001; Clapham and Narbonne,2002; Waggoner, 2003; Grazhdankin, 2004,Narbonne, 2005).
Recent collecting efforts in the AlbemarleGroup of Carolina Terrane by Ruffin Tucker,Tony C. Furr, researchers from the North Caro-lina Museum of Natural Sciences and NorthCarolina State University have yielded addi-tional specimens of Ediacaran body fossils, in-cluding the probable Ediacara holdfast, Sekwiaexcentrica Hofmann, 1981, a possible sac-likeorganism, and Aspidella cf. A. terranovica fromNeoproterozoic rocks of North Carolina.Though Asipidella cf. A. terranovica was men-tioned by Hibbard et al (2006) and Weaver et al(2006b) it was never formally described. Thesenew discoveries combined with previously de-scribed cf. ?Swartpuntia sp. by Weaver et al.(2006a), Pteridinium carolinaensis by St. Jean(1973); Gibson et al. (1984); Gibson and Teeter(2001); and McMenamin and Weaver (2002)and trace fossils such as Planolites described byGibson (1989) give a more complete picture ofthe North Carolina Ediacara biota. The Ediac-ara fossils from the Carolina Terrane are con-sidered a Nama Assemblage because ofsimilarities in age, the presence of Pteridinium(St. Jean, 1973; Gibson et al., 1984; Gibson andTeeter, 2001; McMenamin and Weaver, 2002)and the presence of true trace fossils (Gibson,1989). Thus, though nowhere near as extensiveor complete as many of the other Ediacaran As-semblages world-wide, the Carolina Terranefossils are important as they are a record of adeep-water (Seilacher et al., 2005) Nama As-
ADDITIONAL EDIACARAN BODY FOSSILS OF SOUTH-CENTRAL NORTH CAROLINA
1PATRICIA G. WEAVER, 2R. CHRISTOPHER TACKER, 3MARK A.S. MCMENAMIN, 4CHARLES N. CIAMPAGLIO, AND 5RICHARD A. WEBB
1Geology/Paleontology, North Carolina Museum of Natural Sciences, Raleigh, NC [email protected]
2Geology, North Carolina Museum of Natural Sciences, Raleigh, NC [email protected]
3Department of Geology and Geography, Mount Holyoke College, South Hadley, MA [email protected]
4Department of Geology, Wright State University, Celina, OH [email protected]
5621 Hawick Road, Raleigh, NC [email protected]
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semblage.
GEOLOGIC SETTING
The Carolina Terrane extends from southernVirginia southwest to Georgia and is consideredto be one of several peri-Gondwanan exotic ter-ranes that accreted to the eastern margin of Lau-rentia during the Paleozoic (Hibbard et al.,2002). Rocks within the Carolina Terrane showa lower green-schist facies grade of regionalmetamorphism (Gibson and Huntsman, 1988).Stratigraphic reconstructions of the CarolinaTerrane in North Carolina have undergone a se-ries of revisions and in North Carolina workershave recognized three main stratigraphic units:the Virgilina Sequence, the Uwharrie Forma-tion and the Albemarle Group (Conley, 1962;Conley and Bain, 1965; Stromquist and Sunde-lius, 1969; Seiders, 1978; Milton, 1984) (Figure1). The Albemarle Group has been further sub-divided into Tillery Formation, Cid Formation(consisting of the unnamed Mudstone Memberand the overlying Flat Swamp Member), FloydChurch Formation and Yadkin Formation (Mil-
ton, 1984) from oldest to youngest. Seilacher etal. (2005) considers the Albemarle Group tohave been deposited in deep-water as the for-mations within the group are characterized bythick sequences of laminated mudstones andcoarser-grained turbidites, with an absence ofwave induced structures.
Neoproterozoic Ediacaran body fossils havebeen reported from the Floyd Church Forma-tion (St. Jean, 1973; Gibson et al., 1984; Gibsonand Teeter, 2001; McMenamin and Weaver,2002) and from the unnamed Mudstone Mem-ber of the Cid Formation (Hibbard et al., 2006;Weaver et al., 2006a). Neoproterozoic tracefossils have been reported from most of the Al-bemarle Group except the volcanic Flat SwampMember of the Cid Formation (Gibson, 1989).The new specimen of Sekwia excentrica Hof-mann, 1981 was found lying on the ground onproperty surrounding Gleaning MissionChurch, Stanly County, North Carolina, byRuffin Tucker. Based on rock type and localitythis specimen most likely came from the FloydChurch Formation (Figure 2). Pteridinium car-olinaensis has also been reported from this lo-
Figure 1. Generalized stratigraphic section of the Carolina Terrane exposed in this study area.
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Ediacaran Body Fossils—North Carolina
cale (Gibson and Teeter, 2001; McMenaminand Weaver, 2002). The new specimen of a sac-like organism was found on private propertysoutheast of Cottonville (near Mt. ZionChurch), by Tony C. Furr in the same generalarea from which cf. ?Swartpuntia sp. was re-
ported by Weaver et al. (2006a). Based on rocktype and locality the fossil of this sac-like or-ganism most likely came from the unnamedMudstone Member of the Cid Formation (Fig-ure 2). Aspidella sp. cf. A. terranovica Billings,1872 was recovered from the unnamed Mud-
Figure 2. Map of North Carolina with Stanly County highlighted along with a geologic map ofsouth-central North Carolina (adapted from Goldmith et al., 1988) showing Ediacaran localities(Gibson and Teeter, 2001; Hibbard et al., 2006; Weaver et al., 2006a): 1)Gleaning Mission Church,north of Oakboro, Stanly County, 2) Private property near Mount Zion Church, southeast of Cot-tonville, Stanly County, 3) Jacobs Creek Stone Quarry, Davidson County.
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stone Member of the Cid Formation at the Ja-cob’s Creek Quarry, Davidson County NorthCarolina (Figure 2). Reports of late Cambrianor Ordovician age euconodonts by Koeppen etal. (1995) recovered from the Cid Formation ofthis quarry are considered as either erroneous orrepresentative of structural inliers of Paleozoicsediments on top of Neoproterozoic (Hibbard etal., 2006).
Recent absolute age dating shows the Albe-marle Group to be near the Neoproterozoic-Cambrian boundary (given as 542 +/- 0.3 Ma byAmthor et al., 2003). The ages of the FloydChurch and the unnamed Mudstone Member ofthe Cid Formations are best constrained by re-cent isotopic dates obtained for the Flat SwampMember of the Cid Formation, which has beendated at 547 +/- 2 Ma (Hibbard et al., 2006).The Flat Swamp Member is a distinct markerunit which lies stratigraphically between theoverlying Floyd Church Formation and the un-derlying unnamed Mudstone Member of theCid Formation.
SYSTEMATIC PALEONTOLOGY
All figured specimens are housed at theNorth Carolina Museum of Natural Sciences(NCSM) in Raleigh, North Carolina.
Sekwia excentrica Hofmann, 1981 (Figure 3)
Material__ One specimen, NCSM 9836, pre-served as a cast on the base of a brown sand-stone bed.Description__ Circular fossil approximately 1cm in diameter. A crescentic fold cuts acrossthe fossil to delineate a relatively smooth,roughly elliptical area between the crescenticfold and the edge of the fossil. The elliptical ar-ea has a dimple or crease near its center.
Viewed from stratigraphically below (i.e.,from the underside of the sandstone bed), thefossil sits in a 2 mm depression and has a max-imum relief of approximately 1.3 mm.Locality__ Property surrounding Gleaning Mis-sion Church, Stanly County, North Carolina,Locality 2 of Figure 2, Floyd Church FormationRemarks__ Sekwia excentrica Hofmann, 1981,which Hoffmann originally presumed to belongwith the coelenterates, most likely representsthe remains of a holdfast similar to Aspidella.The crescentic fold that is diagnostic for the ge-nus most likely resulted from the stalk beingtugged, probably by current drag applied to themain body and stalk of the organism.
Although the morphology of this Ediacaranfossil appears to be quite simple, with its circu-lar shape and crescentic fold, the North Caroli-na specimen is a close match to those described
Figure 3. Sekwia excentrica Hofmann, 1981, NCSM 9836 recovered from locality 1 of figure 2.
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Ediacaran Body Fossils—North Carolina
from Sekwi Brook, Mackenzie Mountains byHofmann (1981) as Sekwia excentrica and to aspecimen of Sekwia described from the Clem-ente Formation of Sonora, Mexico (McMe-namin 1996). Both the North Carolina and theSonoran specimens occur on the base of sandbeds, and both have identical diameters andcomparable vertical relief. The new find thusadds considerable confidence to the validity ofthis Proterozoic genus.
McMenamin (2001) had transferred the So-noran Sekwia to the species Beltanelloidessorichevae Sokolov, 1972. However, the clearappearance of the diagnostic crescentic fold inthe North Carolina specimen suggests that Se-kwia is a valid genus in its own right and notmerely a preservational variant of Beltanel-loides. Both the Sonoran and North Carolinaspecimens are hereby assigned to the speciesSekwia excentrica Hofmann, 1981.
Aspidella sp. cf. A. terranovica Billings, 1872 (Figure 4)
Material__ Several specimens, the best ofwhich, NCSM 9713, is preserved as a flatmorph similar to Gehling et al, 2000 text figure5.Description__ The best specimen, NCSM 9713,is preserved as a flat to slightly concave ellipti-
cal disc, with a central concavity less than onequarter of the diameter of the whole disc. Be-tween the rim and the central concavity, the discis either smooth or ornamented with faint con-centric rings near the outer rim. Locality__ Jacob’s Creek Stone Quarry, nearDenton, Davidson County, North Carolina. Lo-cality 3 of Figure 2, unnamed Mudstone Mem-ber of the Cid Formation.Remarks__ This isolated specimen is preservedin a light gray, thinly bedded siltstone. The el-liptical shape of the fossils is most likely the re-sult of regional strain, as the trace of cleavageon bedding is parallel to the long axis of the As-pidella ellipses. Aspidella is thought to repre-sent an “isolated holdfast of perhaps more thanone genus of frond” (Narbonne et al., 2001),and similar considerations may apply to theholdfast fossil Skewia.
Indeterminate Sac-Like Organism (Figure 5)
Material__ one specimen has been recovered ona single float sample (NCSM 8714). The fossilon the rock occurs within several 10-14 mmthick tan to reddish tan mudstone layers. Theupper surface of the fossil is truncated by ero-sion at the top of each layer. The specimen is asac-shaped specimen 23 mm in width.
Figure 4. Aspidella sp. cf. A. terranovica Billings 1872, NCSM 9713 recovered from locality 3 ofFigure 2.
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Description__ Laterally compressed sac-shapedfossil, consisting of a relatively smooth toslightly bulging wall grooved by intersectingsets of sub-parallel to fanned-out grooves. Thegrooves form an ornament on the sac surfacethat, along with the edges of the sac, runs at ahigh angle to bedding.
The grooves are 0.2-0.6 mm in width; wheregrooves are closely spaced and parallel. Theremay be a very narrow groove atop the ridge sep-arating the two major grooves.Locality__ On private property southeast of Cot-tonville (near Mount Zion Church), StanlyCounty, North Carolina, Locality 1 of Figure 2,unnamed Mudstone Member of the Cid Forma-tion.Remarks__ The specimen is 23 mm in width and14 mm in height, but it appears truncated at the
top of the bed that contains it so its originalheight is estimated to have been approximately30-35 mm. It is possible that this specimen rep-resents a ripped up piece of microbial mat.However as the specimen is contained in a fine-ly bedded siltstone with no evidence that thebedding has been disturbed, it is more likelythat this is a sac-like body fossil. Our earlier,tentative identification (Weaver et al. 2006b) ofthis specimen as ?Inaria Gehling, 1988 hasbeen questioned by authorities on this genus (J.Gehling, personal communication, 2006), butnevertheless an attribution to this genus cannotbe definitely ruled out at this point.
CONCLUSIONS
There has been considerable discussion as to
Figure 5. Indeterminate sac-like organism, with line drawing to highlight the fossil, NCSM 9714recovered from locality 2 of figure 2.
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what factors (paleoenvironment, paleobiogeog-raphy, taphonomy, time) might influence as-semblage types during the Late Neoproterozoic(Waggoner, 1999, 2003; Narbonne, 2005).Though the fossil record of Carolina TerraneEdiacara biota is sparse, it may give some in-sight into this on-going discussion. Due to thepresence of Pteridinium, cf. ?Swartpuntia, truetrace fossils and the age of the sediments inwhich these fossils were contained, this biotamost closely matches what has been describedby Waggoner (1999, 2003) as Nama Assem-blage. As the sediments that contain CarolinaTerrane Ediacara fossils are considered to havebeen deposited in much deeper water (Seilacheret al., 2005) than other Nama Assemblages, it ispossible that time has a much stronger influenceon Ediacaran assemblages than environmentalfactors.
ACKNOWLEDGEMENTS
Authors are extremely grateful to North Car-olina Fossil Club members Tony C. Furr andRuffin Tucker for providing specimens for thisstudy, and to Charles Brown, Charles BrownPhotography for photographs of the specimens.We are also grateful to Janet Edgerton for pro-viding bibliographic assistance and to TamaraMoore for assistance with Figure 2. Authors arealso grateful to Dr. James Gehling and anotheranonymous reviewer for their insightful com-ments on an earlier draft of this manuscript andto Dr. Phil Novack-Gottshall and the editors ofSoutheastern Geology for their assistance withthis version of this manuscript.
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